#include "ringbuffer.h"
#include <stdlib.h>

ringbuffer_t
ringbuffer_new(size_t size)
{
	ringbuffer_t buffer = malloc(sizeof(struct ringbuffer_s));
	if(!buffer)
	{
		return NULL;
	}

	buffer->buffer = malloc(sizeof(char) * size);
	if(!buffer->buffer)
	{
		free(buffer);
		return NULL;
	}

	buffer->length = size;
	buffer->head = 0;
	buffer->tail = 0;
	buffer->ovf = 0;
	return buffer;
}

int 
ringbuffer_nonempty(ringbuffer_t buffer)
{
	return (buffer->head != buffer->tail) || buffer->ovf;
}

unsigned char
ringbuffer_get_char(ringbuffer_t buffer)
{
	unsigned char result;
	if((buffer->head == buffer->tail) && !buffer->ovf)
	{
		return 0;
	}
	buffer->ovf = 0;
	result = buffer->buffer[buffer->tail];
	buffer->tail = (buffer->tail + 1) % buffer->length;
	return result;
}

int
ringbuffer_put_char(ringbuffer_t buffer
		, unsigned char c)
{
	if(buffer->ovf)
	{
		return 1;
	}
	buffer->buffer[buffer->head] = c;
	buffer->head = (buffer->head + 1) % buffer->length;
	if(buffer->head == buffer->tail)
	{
		buffer->ovf = 1;
	}
	return 0;
}

size_t ringbuffer_empty_bytes(ringbuffer_t buffer)
{
	if(buffer->ovf)
	{
		return 0;
	}
	int raw_empty = buffer->length - (buffer->head - buffer->tail);
	if(raw_empty > buffer->length)
	{ 
		return raw_empty - buffer->length;
	}
	return raw_empty;
}